001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import static com.google.common.collect.ForwardingSortedMap.unsafeCompare; 020 021import com.google.common.annotations.Beta; 022import com.google.common.annotations.GwtCompatible; 023import java.util.Comparator; 024import java.util.Iterator; 025import java.util.NoSuchElementException; 026import java.util.SortedSet; 027import javax.annotation.CheckForNull; 028import org.checkerframework.checker.nullness.qual.Nullable; 029 030/** 031 * A sorted set which forwards all its method calls to another sorted set. Subclasses should 032 * override one or more methods to modify the behavior of the backing sorted set as desired per the 033 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 034 * 035 * <p><b>Warning:</b> The methods of {@code ForwardingSortedSet} forward <i>indiscriminately</i> to 036 * the methods of the delegate. For example, overriding {@link #add} alone <i>will not</i> change 037 * the behavior of {@link #addAll}, which can lead to unexpected behavior. In this case, you should 038 * override {@code addAll} as well, either providing your own implementation, or delegating to the 039 * provided {@code standardAddAll} method. 040 * 041 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 042 * default} methods. Instead, it inherits their default implementations. When those implementations 043 * invoke methods, they invoke methods on the {@code ForwardingSortedSet}. 044 * 045 * <p>Each of the {@code standard} methods, where appropriate, uses the set's comparator (or the 046 * natural ordering of the elements, if there is no comparator) to test element equality. As a 047 * result, if the comparator is not consistent with equals, some of the standard implementations may 048 * violate the {@code Set} contract. 049 * 050 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be 051 * thread-safe, even when all of the methods that they depend on are thread-safe. 052 * 053 * @author Mike Bostock 054 * @author Louis Wasserman 055 * @since 2.0 056 */ 057@GwtCompatible 058@ElementTypesAreNonnullByDefault 059public abstract class ForwardingSortedSet<E extends @Nullable Object> extends ForwardingSet<E> 060 implements SortedSet<E> { 061 062 /** Constructor for use by subclasses. */ 063 protected ForwardingSortedSet() {} 064 065 @Override 066 protected abstract SortedSet<E> delegate(); 067 068 @Override 069 @CheckForNull 070 public Comparator<? super E> comparator() { 071 return delegate().comparator(); 072 } 073 074 @Override 075 @ParametricNullness 076 public E first() { 077 return delegate().first(); 078 } 079 080 @Override 081 public SortedSet<E> headSet(@ParametricNullness E toElement) { 082 return delegate().headSet(toElement); 083 } 084 085 @Override 086 @ParametricNullness 087 public E last() { 088 return delegate().last(); 089 } 090 091 @Override 092 public SortedSet<E> subSet(@ParametricNullness E fromElement, @ParametricNullness E toElement) { 093 return delegate().subSet(fromElement, toElement); 094 } 095 096 @Override 097 public SortedSet<E> tailSet(@ParametricNullness E fromElement) { 098 return delegate().tailSet(fromElement); 099 } 100 101 /** 102 * A sensible definition of {@link #contains} in terms of the {@code first()} method of {@link 103 * #tailSet}. If you override {@link #tailSet}, you may wish to override {@link #contains} to 104 * forward to this implementation. 105 * 106 * @since 7.0 107 */ 108 @Override 109 @Beta 110 protected boolean standardContains(@CheckForNull Object object) { 111 try { 112 // any ClassCastExceptions and NullPointerExceptions are caught 113 @SuppressWarnings({"unchecked", "nullness"}) 114 SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this; 115 Object ceiling = self.tailSet(object).first(); 116 return unsafeCompare(comparator(), ceiling, object) == 0; 117 } catch (ClassCastException | NoSuchElementException | NullPointerException e) { 118 return false; 119 } 120 } 121 122 /** 123 * A sensible definition of {@link #remove} in terms of the {@code iterator()} method of {@link 124 * #tailSet}. If you override {@link #tailSet}, you may wish to override {@link #remove} to 125 * forward to this implementation. 126 * 127 * @since 7.0 128 */ 129 @Override 130 @Beta 131 protected boolean standardRemove(@CheckForNull Object object) { 132 try { 133 // any ClassCastExceptions and NullPointerExceptions are caught 134 @SuppressWarnings({"unchecked", "nullness"}) 135 SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this; 136 Iterator<?> iterator = self.tailSet(object).iterator(); 137 if (iterator.hasNext()) { 138 Object ceiling = iterator.next(); 139 if (unsafeCompare(comparator(), ceiling, object) == 0) { 140 iterator.remove(); 141 return true; 142 } 143 } 144 } catch (ClassCastException | NullPointerException e) { 145 return false; 146 } 147 return false; 148 } 149 150 /** 151 * A sensible default implementation of {@link #subSet(Object, Object)} in terms of {@link 152 * #headSet(Object)} and {@link #tailSet(Object)}. In some situations, you may wish to override 153 * {@link #subSet(Object, Object)} to forward to this implementation. 154 * 155 * @since 7.0 156 */ 157 @Beta 158 protected SortedSet<E> standardSubSet( 159 @ParametricNullness E fromElement, @ParametricNullness E toElement) { 160 return tailSet(fromElement).headSet(toElement); 161 } 162}